This invention relates to methods of treating wastes, and more particularly methods of neutralizing and detoxifying wastes containing acids and toxic organic compounds.
Many industrial processes produce waste materials which include toxic organic compounds dissolved in acids. Typical acids include sulfuric, hydrochloric, and nitric acid; and typical organic compounds include dichlorobenzidine, orthochloraniline, and polychlorinated biphenyl. Disposal of such waste materials is complicated due to the presence of both the acids and the toxic organic compounds. Although the waste materials may be hauled to a toxic disposal site, such transportation and disposal is extremely expensive.
Most typically, waste materials containing acids are neutralized and pumped to a settling pond, comprising a pit, preferably clay-lined, into which the neutralized material is placed. Concentrated caustic, such as calcium hydroxide, calcium oxide, or sodium hydroxide, is mixed with the material to neutralize the acid, producing an extremely thick salt slurry which, because of its viscosity, may not be completely neutralized. The neutralized material may be periodically hauled to a toxic disposal site. However, if the settling pond is not carefully lined, both the toxic organic compounds and the remaining acids can leach into the ground water, rendering the same non-potable. For this and other reasons, many states now prohibit settling ponds of this type and require that existing ponds be eliminated.
Alternatively, the toxic, acidic materials may be burned to destroy the organic compounds. More particularly, government regulations state that subjecting the toxic organics to a temperature of 2200.degree. F. for a period of two seconds presumably destroys all toxic compounds. However, the acids in the waste material must be neutralized before the material is burned, producing a liquid salt stream, which is extremely difficult to handle. Water must be distilled off the waste material prior to burning, or the burning operation produces a high-volume gas stream which must be scrubbed at high expense. Such distillation is extremely difficult and also relatively expensive. Alternatively, prior to burning, the waste material may be neutralized, as in settling ponds, in which case the material becomes extremely thick and difficult to handle due to the precipitation of salts, such as calcium sulfate, calcium chloride, and calcium nitrate, creating an extremely thick, non-pumpable salt slurry. Large quantities of water must be mixed with the neutralized material in order to transport the material to the burner. This water must then be distilled off the mixture prior to burning or handled as a high-volume gas stream after burning, with the attendant, virtually prohibitive costs discussed above.